Five points: 【Bluetooth 5.1 Audio Adapter】You can listen to music on your smartphone or tablet with a sound system that has perfect sound quality. Compared to Bluetooth 5.0, it achieves more stable audio transmission, lower audio delay, and better noise canceling. 【Excellent Acoustic Performance】No compromise on sound. Press the 3D button to switch the 3D surround mode on/off. The 3D surround mode (LED remains green) provides a stronger and deeper sound experience. You can enjoy hi-fi surround sound from normal audio sources. 【2 in 1 Bluetooth Transmitter & Receiver】The Aux Bluetooth adapter supports audio transmission with a transmission function (TX) to headphones and a receiving function (RX) to car stereos and stereo systems. The Bluetooth communication distance is up to 15m (when there are no obstacles). The Bluetooth Aux adapter has an automatic connection memory function. 【Long Playback and Easy Setup】The Bluetooth adapter stereo can be used for up to 12 hours on a single charge (only 2 hours to fully charge). It also supports charging during use. Setup is very easy, just plug in, pair, and play. The Bluetooth adapter Aux has a built-in microphone and an "MFB" button for play/pause/call, so you can make hands-free calls. 【Strong Compatibility】The Bluetooth stereo receiver has two interfaces. It supports all stereo systems with a jack or RCA jack. It automatically turns off after 10 minutes without a Bluetooth connection, making it ideal for home audio and car audio.